We stock fenced the perimeter of our holding and have divided it into paddocks with electric fencing. We use 40mm tape high level for the horses and 3 lines of rope lower down for the sheep, all tensioned between wooden posts and supported with poly posts. This keeps the fence tight but is easy to take down and move.
Our sheep are mostly Greyfaced Dartmoors which have a very thick fleece so we upgraded the energiser to produce around 8kV which is definitely enough for a sheep to notice. They know exactly where the lines are and avoid them. I think keeping good tension in the ropes and tapes is important cos I've seen a ewe lean on one for several seconds before getting a shock. You also don't want an animal to able to get caught in the fence either.
If lambs can get through then mum is likely to try to follow, so it's best for the lambs to learn about the fence quickly and avoid it.